A sprinkler head is installed on a ceiling surface or a wall surface in a building, and includes a nozzle which can be connected to piping continuing to a water supply at one end thereof, and a thermosensitive operating portion at the other end thereof. At a non-emergency time, the thermosensitive operating portion supports a valve body configured to close the nozzle.
As an example of the sprinkler head, there is a concealed sprinkler head configured to be installed in a state of being embedded in a ceiling surface or a wall surface, in which the sprinkler head is hidden and covered by a cover plate. The concealed sprinkler head is used as a sprinkler head that is superior in terms of design and, for example, there is the one described in Patent Literature 1. The concealed sprinkler head in Patent Literature 1 is provided with a cylindrical member on the outer portion of a so-called frame yoke type sprinkler head, which includes a horseshoe-shaped frame extending from a terminal end of the nozzle and a deflector installed on an extension portion of the nozzle, and an engaging portion for the cover plate provided on a lower portion of the cylindrical member.
A sprinkler head illustrated in FIG. 12 has a similar structure to the concealed sprinkler head of Patent Literature 1, in which a cylindrical member A is provided outside a frame yoke type sprinkler head SH (hereinafter referred to as “sprinkler head SH”), and a cylindrical retainer B having a cover plate P joined thereto by a low melting point alloy is connected to the lower portion of the cylindrical member A.
As a structure of a connecting portion between the cylindrical member A and the retainer B, a helical groove A1 formed in the lower portion of the cylindrical member A and a projection B1 formed so as to project from an outer peripheral surface of the retainer B are configured to be capable of being engaged with each other by being screwed together.
The sprinkler head SH, the cylindrical member A, and the retainer B are arranged on the back side of the ceiling, and only the cover plate P is arranged in the vicinity of the ceiling surface. Since the cover plate P is connected to the retainer B by the low melting point alloy, the cover plate P drops due to heat generated in case of fire. Dropping of the cover plate P exposes the sprinkler head SH.
When the sprinkler head SH is exposed, subsequently, a thermosensitive operating portion G of the sprinkler head SH is operated and destroyed to release the valve body in the interior of the sprinkler head SH, so that water is sprinkled from the sprinkler head SH to extinguish the fire.
Patent Literature 1: U.S. Pat. No. 4,014,388